Bicycle hydraulic assembly and bicycle brake device

A bicycle hydraulic assembly, configured to accommodate an oil, comprising:

• a casing, having a hydraulic chamber, an inlet channel, and an outlet channel, wherein the inlet channel and the outlet channel are connected to the hydraulic chamber;
• a first piston, movably located in the hydraulic chamber;
• and
• a second piston, movably located in the hydraulic chamber and sleeved on the first piston, wherein the second piston has a first end portion and a second end portion located opposite to each other, an outer diameter of the first end portion is greater than an outer diameter of the second end portion, and the second end portion is located farther away from the inlet channel than the first end portion;
• wherein when the first piston is moved a distance smaller than a threshold distance by the oil, the first piston is moved relative to the second piston while the second piston is stationary relative to the casing;
• wherein when the first piston is moved a distance greater than the threshold distance by the oil, the first piston forces the second piston to move relative to the casing;
• wherein the hydraulic chamber has a first chamber and a second chamber connected to each other, a width of the first chamber is greater than a width of the second chamber, the first chamber is located closer to the inlet channel than the second chamber, the inlet channel and the outlet channel are respectively connected to the first chamber and the second chamber, different portions of the first piston are respectively located in the first chamber and the second chamber, the first end portion and the second end portion of the second piston are respectively located in the first chamber and the second chamber, the second piston has a through hole, the first piston is disposed through the through hole of the second piston;
• when the first piston is moved the distance smaller than the threshold distance by the oil, the inlet channel is in fluid communication with the second chamber via the through hole of the second piston;
• when the first piston is moved a distance equal to the threshold distance by the oil, the first piston blocks the through hole, such that the inlet channel is not in fluid communication with the second chamber.